| A large amount of coal is exposed to the external environment for a long time during the stacking process,and an exothermic oxidation reaction will occur,which releases a lot of heat.When heat builds up to a certain degree,it will cause the coal pile to ignite spontaneously.Although China is a big coal producing country,the existing coal mining methods,as well as coal storage and transportation methods are still not perfect.Based on this,in order to prevent spontaneous combustion of coal piles,gravity heat pipe was used to remove heat and cool in this paper.A gravity heat pipe was inserted inside the coal pile.Because of the high thermal conductivity of the heat pipe phase change,heat accumulated in the coal pile would be extracted timely.Based on energy conservation and environmental protection,the method of effectively utilizing the heat accumulated in the coal piles was studied in this paper.Based on improving the heat dissipation efficiency of loose coal,mathematical models of single heat pipe,two heat pipes and inclined pipe cooling to coal piles were established in this paper.The reason for the spontaneous combustion of coal piles were explained in detail.On this basis,the influence of the heat pipe inserted into the coal pile under different depths,angles and spacings on the temperature field and humidity field of the coal pile was simulated numerically.In addition,based on the Seebeck effect,a thermoelectric energy conversion system was designed to convert the heat energy absorbed by the gravity heat pipe from the inside of the coal into electrical energy to supply the use of low-power components.The results show that when a single gravity heat pipe is used for heat transfer and cooling,if the heat pipe is inserted into the coal pile to a large depth(0.35 m),and the inclination angle is 70°,the heat pipe has a better cooling effect.At the same time,the the closer the loose coal is to the heat pipe,the lower the temperature will be.The numerical simulation results within the radius of influence of the heat pipe are consistent with the mathematical model inference.When two gravity heat pipes are used for heat transfer and cooling,during the change of heat pipe spacing from 0.05 m to 0.25 m,the maximum temperature drop values of the coal body at the 0.05 m and 0.15 m above the heat source are 36.55 K and 40.47 K respectively.When the heat pipe spacing is 0.15 m,the temperature rise of the coal pile can be effectively suppressed,which is the optimal arrangement spacing in practical application.What's more,when studying the influence of the gravity heat pipe on the humidity field of the coal pile,it was found that the higher the temperature is,the lower the humidity will be.The humidity at the bottom of the high temperature zone of the heat source is first reduced,followed by the sides of the heat source,and finally the upper side of the heat source.The cooling effect on both sides of the gravity heat pipe is better,and the humidity value is slightly higher.Figure [38] table [7] reference [63]... |
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